Disc drive machines record and reproduce information stored on magnetic media. Conventional Winchester-type disc drives include a plurality of vertically aligned rotating information storage discs journaled about a spindle motor assembly within a housing. Magnetic discs which are of the type used as such storage media typically each have at least one associated head that is adapted to transfer information between the disc and an external system. Each head is carried by an elongated flexure arm. The flexure arms are vertically aligned and are each attached to a common head positioner assembly. The head positioning assembly is adapted to move the heads back and forth in unison across the face of the vertically aligned discs. The head positioner assembly may be either rotationally actuated along an arc, or take the form of a linear carriage that is free to move back and forth along a single axis, although the rotational actuator is the approach more commonly employed in today's disc drive designs.
In either case, the head positioner assembly is adapted to rapidly and precisely position the heads relative to the magnetic discs. Rapid movement of the various components, including the rotating spindle motor, the head positioner assembly, and the discs themselves tends to generate a wide variety of undesirable acoustic vibrations within the disc drive.
A primary source of acoustical emissions from a disc drive is the amplification of these vibrations and especially of the spindle motor vibration by the top cover and the base of the disc drive. One method of reducing the amplification of the cover is to add damping directly to the cover. Past tests have considered applying a constrain damping layer material to an existing cover. This approach was not successful unless the material was a lead sheet, which is environmentally toxic and expensive.
Therefore other approaches must be considered which are more effective in damping out the vibrations which are amplified and broadcast by the loudspeaker.
Further efforts to reduce noise emissions from the disc drive must be focused on reducing the amplification caused by vibration of the printed circuit board which is suspended below the base of the typical disc drive. This printed circuit board (PCB) being highly flexible, is a significant source of amplification of spindle motor noise. It is unacceptable to continue to have such significant noise emissions from commercial products which are used in computers which have few other noise sources, making the noise emissions from the disc drive irritating and undesirable.